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Duplicated Genes on Homologous Chromosomes Decipher the Dominant Epistasis of the Fiberless Mutant in Cotton
by
,
Yu Le
1
,
Xingchen Xiong
1,
Zhiyong Xu
1,
Meilin Chen
1,
Yuanxue Li
1,
Chao Fu
1,
Chunyuan You
2,* and
Zhongxu Lin
1,3,*
1
National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
2
Cotton Research Institute, Shihezi Academy of Agriculture Science, Shihezi 832011, China
3
Xinjiang Uygur Autonomous Region Academy of Agricultural Sciences, Urumqi 830091, China
*
Authors to whom correspondence should be addressed.
Biology 2025, 14(8), 983; https://doi.org/10.3390/biology14080983 (registering DOI)
Submission received: 22 June 2025
/
Revised: 16 July 2025
/
Accepted: 29 July 2025
/
Published: 2 August 2025
(This article belongs to the Special Issue Cotton: Genomics, Biotechnology and Molecular Breeding)
Simple Summary
Cotton produces two distinct types of seed fibers: short fuzz and long lint, with lint fiber initiation being the primary determinant of cotton yield as the world’s most important natural textile source. However, the genetic regulation underlying fiber initiation exhibits considerable complexity. This study characterized the mutant loci responsible for the fiberless (fuzzless–lintless, seeds without both lint and fuzz) phenotype in a naturally fiberless cotton mutant (fblSHZ), identifying duplicated GhMYB25like genes on homologous Chr A12 and Chr D12 as key regulators of both lint and fuzz fiber initiation. Genetic analysis revealed a dominant epistasis with the fuzz gene exerting dominance over the lint gene. Furthermore, the study demonstrated that these genes influence fiber initiation through multiple biological processes, particularly fatty acid metabolism. These findings provide fundamental insights into the genetic mechanisms governing cotton fiber initiation, offering valuable theoretical foundations for yield improvement in cotton breeding.
Abstract
Cotton fiber initiation determines the fiber yield, yet the genetic basis underlying lint and fuzz initiation has still not been fully uncovered. Here, map-based cloning was carried out to identify the fiberless mutant genes derived from a cross between Gossypium hirsutum acc. WT and a natural fiberless mutant, fblSHZ. The 12:3:1 segregation ratio in F2 populations (including 1848 and 3100 individuals that were developed in 2016 and 2018, respectively) revealed dominant epistasis, with the fuzz gene exerting dominance over the lint gene. Genetic linkage analysis revealed that GhMYB25like_A12 controls fuzz fiber initiation, while both GhMYB25like_A12 and GhMYB25like_D12 regulate lint fiber development. Sequencing analyses showed that the fblSHZ mutant exhibited a K104M mutation in the R2R3 domain of GhMYB25like_A12 and a transposable element insertion in GhMYB25like_D12, leading to fiberless seeds. Knockout of GhMYB25like_A12 produced fuzzless seeds, knockout of GhMYB25like_D12 led to no obvious change in seeds, and knockout of both (GhMYB25like_A12&D12) resulted in fiberless seeds. The 12:3:1 ratio reappeared in the F2 population developed from the GhMYB25like_A12&D12 mutated plants as female and Jin668 as the male, which further confirmed the genetic interaction observed in fblSHZ. RNA-seq analysis revealed that GhMYB25like regulates cotton fiber initiation through multiple pathways, especially fatty acid metabolism. This study elucidates the key genes and their genetic interaction mechanisms governing cotton fiber initiation, providing a theoretical foundation for genetic improvement of cotton fiber traits.
Keywords:
cotton; fiber initiation; GhMYB25like; dominant epistasis; RNA-seq
